PostgreSQL is an open source, community driven, standard compliant object-relational database system.

This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. Among other applications, PostgreSQL can be substituted for MySQL as part of the LAMP web stack.

Tip: If you change the root to something other than /var/lib/postgres, you will have to edit the service file. If the root is under home, make sure to set ProtectHome to false.

Warning: If the database resides on a Btrfs file system, you should consider disabling Copy-on-Write for the directory before creating any database. If the database resides on a ZFS file system, you should consult ZFS#Database before creating any database.

Create your first database/user

Tip: If you create a PostgreSQL user with the same name as your Linux username, it allows you to access the PostgreSQL database shell without having to specify a user to login (which makes it quite convenient).

Become the postgres user. Add a new database user using the createuser command:

[postgres]$ createuser --interactive

Create a new database over which the above user has read/write privileges using the createdb command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add -U database-username to the following command):

$ createdb myDatabaseName

Familiarize with PostgreSQL

Access the database shell

Become the postgres user. Start the primary database shell, psql, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the -d option to connect to the database you created (without specifying a database, psql will try to access a database that matches your username).

[postgres]$ psql -d myDatabaseName

Some helpful commands:

Get help:

=> \help

Connect to a particular database:

=> \c <database>

List all users and their permission levels:

=> \du

Show summary information about all tables in the current database:

=> \dt

Exit/quit the psql shell:

=> \q or CTRL+d

There are of course many more meta-commands, but these should help you get started. To see all meta-commands run:

=> \?

Optional configuration

Configure PostgreSQL to be accessible from remote hosts

The PostgreSQL database server configuration file is postgresql.conf. This file is located in the data directory of the server, typically /var/lib/postgres/data. This folder also houses the other main configuration files, including the pg_hba.conf.

Note: By default, this folder will not be browsable or searchable by a regular user. This is why find and locate are not finding the configuration files.

Edit the file /var/lib/postgres/data/postgresql.conf. In the connections and authentications section, add the listen_addresses line to your needs:

listen_addresses = 'localhost,my_local_ip_address'
#You can use '*' to listen on all local addresses

Take a careful look at the other lines.

Host-based authentication is configured in /var/lib/postgres/data/pg_hba.conf. This file controls which hosts are allowed to connect. Note that the defaults allow any local user to connect as any database user, including the database superuser. Add a line like the following:

# IPv4 local connections:
host all all my_remote_client_ip_address/32 md5

After this you should restartpostgresql.service for the changes to take effect.

Note: PostgreSQL uses port 5432 by default for remote connections. Make sure this port is open and able to receive incoming connections.

For troubleshooting take a look in the server log file:

$ journalctl -u postgresql

Configure PostgreSQL authenticate against PAM

PostgreSQL offers a number of authentication methods. If you would like to allow users to authenticate with their system password, additional steps are necessary. First you need to enable PAM for the connection.

For example, the same configuration as above, but with PAM enabled:

# IPv4 local connections:
host all all my_remote_client_ip_address/32 pam

The PostgreSQL server is however running without root privileges and will not be able to access /etc/shadow. We can work around that by allowing the postgres group to access this file:

setfacl -m g:postgres:r /etc/shadow

Change default data directory

The default directory where all your newly created databases will be stored is /var/lib/postgres/data. To change this, follow these steps:

If you want to use /home directory for default directory or for tablespaces, add one more line in this file:

ProtectHome=false

Change default encoding of new databases to UTF-8

Note: If you ran initdb with -E UTF8 these steps are not required.

When creating a new database (e.g. with createdb blog) PostgreSQL actually copies a template database. There are two predefined templates: template0 is vanilla, while template1 is meant as an on-site template changeable by the administrator and is used by default. In order to change the encoding of a new database, one of the options is to change on-site template1. To do this, log into PostgreSQL shell (psql) and execute the following:

First, we need to drop template1. Templates cannot be dropped, so we first modify it so it is an ordinary database:

Upgrading PostgreSQL

From version 10.0 onwards PostgreSQL changed its versioning scheme. Earlier upgrade from version 9.x to 9.y was considered as major upgrade. Now upgrade from version 10.x to 10.y is considered as minor upgrade and upgrade from version 10.x to 11.y is considered as major upgrade.

Warning: The following instructions could cause data loss. Use at your own risk.

It is recommended to add the following to your /etc/pacman.conf file:

IgnorePkg = postgresql postgresql-libs

This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in pacman.conf. Minor version upgrades (e.g. 9.0.3 to 9.0.4) are safe to perform. However, if you do an accidental upgrade to a different major version (e.g. 9.0.x to 9.1.x), you might not be able to access any of your data. Always check the PostgreSQL home page to be sure of what steps are required for each upgrade. For a bit about why this is the case, see the versioning policy.

There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.

For those wishing to use pg_upgrade, a postgresql-old-upgrade package is available that will always run one major version behind the real PostgreSQL package. This can be installed side-by-side with the new version of PostgreSQL.

When you are ready, upgrade the following packages: postgresql, postgresql-libs, and postgresql-old-upgrade. Note that the data directory does not change from version to version, so before running pg_upgrade, it is necessary to rename your existing data directory and migrate into a new directory. The new database must be initialized, as described near the top of this page.

pg_upgrade will perform the upgrade and create some scripts in /var/lib/data/postgres/tmp. Follow the instructions given on screen and act accordingly. You may delete /var/lib/data/postgres/tmp directory once the upgrade is completely over.

Troubleshooting

Improve performance of small transactions

If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning synchronous_commit off in the configuration. Beware of the caveats, however.

/var/lib/postgres/data/postgresql.conf

synchronous_commit = off

Prevent disk writes when idle

PostgreSQL periodically updates its internal "statistics" file. By default, this file is stored on disk, which prevents disks from spinning down on laptops and causes hard drive seek noise. It is simple and safe to relocate this file to a memory-only file system with the following configuration option:

/var/lib/postgres/data/postgresql.conf

stats_temp_directory = '/run/postgresql'

Cannot connect to database through pg_connect()

Install php-pgsql and edit the php.ini file uncommenting the lines extension=pdo_pgsql.so and extension=pgsql.so, then restart httpd.